1. Field of the Invention
The present invention relates to a human body sensing device capable of identifying the location and/or movement of a human body and an image forming apparatus with such a human body sensing device being installed thereon.
2. Description of the Related Art
The following description sets forth the inventor's knowledge of related art and problems therein and should not be construed as an admission of knowledge in the prior art.
Some of the image forming apparatuses such as copiers, printers, and facsimiles, and some of the multifunctional digital image forming apparatuses referred to as MFPs (Multi Function Peripherals) collectively having copier, printer, and facsimile functions and the like are provided with a human body sensing device for sensing a human body moving toward themselves, so that they immediately can exit sleep mode to get back to normal operation mode for a warm-up operation when a human body is moving toward themselves.
For example, there commonly known is a human body sensing device consisting of a pyroelectric infrared sensor with an energy-saving and low-cost configuration, capable of performing human body sensing.
It is advantageous for such a pyroelectric infrared sensor, if it is installed on the ceiling, to detect a human body on the floor; the pyroelectric infrared sensor is very good at detecting a human body moving across the sensing zone based on a change in temperature over there. To the contrary, it is not so advantageous for such a pyroelectric infrared sensor, if it is installed on the image forming apparatus, to detect a human body (a user) moving toward the image forming apparatus with the intention to use it; the pyroelectric infrared sensor is not very good at detecting a human body moving against the front direction of the pyroelectric infrared sensor itself based on a change in temperature in the sensing zone, because such a change is always too small. In this case, from which direction a human body enters the sensing zone and whether or not a human body is taking a pause cannot be recognized.
To avoid this trouble, Japanese Patent Application H06-059039 discloses a technology to identify the location of a human body by rotating a ring-shaped shield plate with through-holes, which is provided outside of a sensor, about the axis of the sensor.
However, the technology disclosed in the publication above can detect a human body who is in the sensing zone of the sensor but cannot identify the location and/or movement of the human body accurately, for example whether toward or away from the sensor the human body is moving.
The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present invention. Indeed, certain features of the invention may be capable of overcoming certain disadvantages, while still retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.